Mechanism of miR-21 in delayed ischemia preconditioning and its protection against subsequent ischemia reperfusion injury in kidney

Objective To investigate the molecular mechanism of protection of ischemia preconditioning on renal ischemia reperfusion injury. Methods Male C57/BL6N mice were randomly divided into two groups: in IR group, 35 min ischemia was induced by occlusion of both renal pedicles followed by 24 h perfusion (I/R). 15 min ischemia was induced 4 days before I/R in IPC group. Blood sample and kidney were collected in IR and IPC group after 24 h perfusion. Serum creatinine (Scr) and histological changes were used to evaluate the renal injury. PHD2 and HIF-1α were evaluated by Western blotting, miR-21 expression was confirmed by real-time PCR. In vitro, hypoxic model was established by 1% O2 in HK-2 cells. Knockdown of miR-21 in hypoxic model was perfermed by locked nucleic acid modified-anti-miR-21 transfection. The levels of miR-21, HIF-1α and PHD2 mRNA were confirmed by real-time PCR. The levels of HIF-1α and PHD2 proteins were tested by Western blotting. Results In vivo, Compared with IR group, the renal function and histological changes were improved in IPC group (P＜0.01). Compared with IR group, the expression of miR-21(P＜0.01) and HIF-1α (P＜0.05) were increased in IPC group, while PHD2 was reduced (P＜0.01). In vitro, hypoxia reduced miR-21. The inhibition of miR-21 could increased the expression of PHD2 (P＜0.05). Conclusions Ischemia preconditioning may exert protection against renal ischemia reperfusion injury by inhibiting PHD2.     

肾脏缺血预适应及细胞间黏附分子1的作用

目的建立肾脏缺血预适应大鼠模型,探讨缺血预适应对细胞间黏附分子(ICAM)-1mRNA表达的影响。方法摘除右肾后,对左肾采用2min缺血 5min再灌注,4个循环后再缺血45min,建立大鼠肾脏缺血预适应模型。RT-PCR检测肾脏ICAM-1mRNA表达。结果缺血预适应使肾缺血后Scr的升高幅度值减少,肾小管损伤减轻,髓质ICAM-1mRNA表达降低。结论肾脏缺血预适应可从组织学和功能上减轻肾脏的急性缺血性损伤,这可能与肾组织ICAM-1表达降低及局部炎症减轻有关。     

Activation of protein kinase C delta reduces hepatocellular damage in ischemic preconditioned rat liver

Background

Liver ischemic preconditioning (IPC), pre-exposure of the liver to transient ischemia, has been applied as a useful surgical method to prevent liver ischemia and reperfusion (I/R) injury. Although activation of protein kinase C (PKC), especially novel PKCs, has been known as central signaling responsible for the liver protection of IPC, determination of the involved isozyme in strong protection afforded by IPC has not been elucidated.

Materials and methods

Rats were subjected to 90 min of partial liver ischemia followed by 3, 6, and 24 h of reperfusion. IPC was induced by 10 min of ischemia after 10 min of reperfusion before sustained ischemia. Rottlerin, a PKC-δ selective inhibitor; PKC-εV1-2 peptide, a selective PKC-ε inhibitor; and 3,7-dimethyl-1-[2-propargyl] xanthine, an adenosine A₂ receptor antagonist, were intravenously injected before IPC. N-acetyl-L-cysteine, a strong antioxidant, and Nω-nitro-L-arginine methyl ester, a nonselective nitric oxide synthase inhibitor, were injected intraperitoneally before IPC.

Results

IPC resulted in strong protection against liver I/R injury as evidenced by biochemical and histologic analyses. Inhibition of PKC-δ strongly attenuated the IPC-induced liver protection, whereas PKC-ε inhibition did not exert any effect on IPC-induced protection. Although inhibition of reactive oxygen species, adenosine, and nitric oxide attenuated the beneficial effects of IPC, inhibition of adenosine only attenuated PKC-δ and -ε translocation.

Conclusions

Our findings suggest that IPC protects against I/R-induced hepatic injury through activation of PKC-δ.     

Ischemic preconditioning prevents apoptotic cell death and necrosis in early and intermediate phases of liver ischemia-reperfusion injury in rats.

Ischemic preconditioning (IPC) may be useful in attenuating the hepatic ischemia reperfusion (IR) syndrome by means of improving cell resistance to anoxia and reoxygenation and preventing cell death. Since there are insufficient data available regarding the chronology of preconditioning effects, we investigated the role of IPC, to test the hypothesis that liver protection would occur during the early and intermediate phases of the reperfusion period. Wistar rats (n = 72) were randomly assigned into six experimental groups, 12 animals each. A 40-min ischemia to the left lateral and median liver lobes was induced by selective hepatic pedicle clamping followed by 30 min or 240 min of reperfusion (IR30 and IR240). IPC groups (IPC30 and IPC240) underwent a 10 min of ischemia followed by 10 min of reperfusion preceding the definitive 40-min ischemic period. Sham-operated animals were followed for 30 and 240 min. Hepatic enzymes and histological evaluation were performed after the reperfusion period. Hepatic ischemia-reperfusion (IR30 and IR240) induced marked increases in liver enzymes levels after 30 min and particularly after 240 min. IPC effectively attenuated those enzymatic increases. Microvesicular steatosis was observed after 30 min, but not 240 min, of reperfusion in both IPC and IR livers. Necrosis was detected in 66.7% of IR240 and only in 8.3% of IPC240. Both hepatocyte and sinusoidal apoptosis were markedly attenuated by IPC. We conclude that IPC provided protection against hepatic ischemia reperfusion injury in early and intermediate phases of the reperfusion period, reducing hepatic enzymatic leakage and ameliorating hepatic apoptosis and necrosis.     

Initiation of microvascular protection by nitric oxide in late preconditioning

The authors hypothesized that nitric oxide is induced by a brief period of ischemia/reperfusion (ischemic preconditioning, IPC) on postoperative day (POD) 1, and that this released nitric oxide is responsible for initiating a delayed microvascular protection against a prolonged period of ischemia in skeletal muscle on POD day 2. The cremaster muscle of male Sprague-Dawley rats underwent 4 hr of ischemia, and then 60 min of reperfusion. IPC consisted of 45 min of ischemia but was done 24 hr before the prolonged ischemia. Local intraarterial infusion of sodium nitroprusside (SNP, a donor of nitric oxide) or Nw-nitro-L-arginine (L-NA, a nonselective nitric oxide synthase antagonist) were also given 24 hr before prolonged ischemia. Arteriole diameters and capillary perfusion were measured using intravital microscopy. Four groups were compared: 1) control; 2) IPC; 3) SNP + sham IPC; and 4) L-NA + IPC. Four hours of ischemia followed by reperfusion created a significant vasoconstriction and capillary no-reflow in the microcirculation of cremaster muscles. These alterations were largely prevented by IPC. Local intraarterial infusion of SNP without IPC created a similar microvascular protection to that induced by IPC alone. In contrast, intraarterial infusion of L-NA prior to IPC eliminated the IPC-induced microvascular protection. In conclusion, in late preconditioning, nitric oxide contributes to the initiation of a delayed microvascular protection against prolonged ischemia in skeletal muscle.     

缺血预处理对大鼠肝脏缺血/再灌注损伤的延迟保护作用及机制

目的 研究缺血预处理(IPC)对大鼠肝脏缺血/再灌注损伤的延迟保护作用,并探讨线柱体ATP敏感性钾通道(mitoKATP通道)在这种保护机制中的作用. 方法 SD大鼠随机分为5组(每组8只).IPC组以肝缺血5 min作预处理;DE组以静脉注射mitoKATP通道选择性开放剂二氮嗪(DE)作为预处理;IPC+5-HD组是在IPC组基础上再予静注mitoKATP通道特异性阻滞剂5-hydroxydecanoate(5-HD)进行预处理;对照组(C组)仅以静注等量生理盐水作为预处理;上述4组均在预处理24 h后行肝缺血1 h再灌注3 h,缺血方式均为70%肝脏热缺血.假手术组(S组)仅行两次开腹手术,不作其它处理.完成预定实验操作后取血用于血清谷丙转氨酶(ALT)与乳酸脱氢酶(LDH)检测,切取肝组织用于测定超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量、湿重/干重(W/D)及观察显微及超微结构变化. 结果 C组ALT,LDH,MDA及W/D值明显高于S组(P<0.01),而SOD活性明显低于S组(P<0.01),肝脏的显微及超微结构损伤明显;IPC组与DE组的各项肝损伤指标均明显好于C组(P<0.05及P<0.01);IPC+5-HD组的肝损伤指标均差于IPC组(P<0.05及P<0.01). 结论 缺血预处理对正常大鼠肝脏I/R损伤具有延迟保护作用,肝细胞mitoKATP通道的开放在其中发挥了重要作用,作用途径可能与诱导肝脏SOD活性增加,改善肝组织微循环,减轻肝脏水肿有关.     

Delayed energy protection of ischemic preconditioning on hepatic ischemia/reperfusion injury in rats

BACKGROUND: Hepatic ischemia/reperfusion (IR) injuries associated with hepatic resections are unresolved problems in the clinical practice. The aim of this study is to elucidate the effect of ischemic preconditioning (IPC) on the energy charge (EC) and related mechanisms at the late phase of hepatic IR injury. METHODS: 30 Wistar rats were randomly divided into sham, IR and IPC groups. The model of partial hepatic IR was used. The rats were subjected to 60 min hepatic ischemia, pretreated by IPC (10/15 min) or not. After 24 h of reperfusion, serum alanine aminotransferase (ALT), nitrite/nitrate (NOx), malondialdehyde (MDA), hepatic tissue arginase activity, adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and EC of the liver were measured. RESULTS: Liver injury reduced by IPC is measured by liver tissue arginase activity and serum ALT. Tissue NOx levels in rats pretreated with IPC were significantly higher than levels in the IR group (p < 0.001). Tissue levels of MDA in the liver of the IPC group were found to be significantly lower than the levels in the IR group (p < 0.001). ATP and EC levels 24 h after hepatic ischemia in rats pretreated with IPC were higher than the levels in the IR (p < 0.05). All groups had similar ADP and AMP levels in the liver tissues. The IPC procedure significantly reduced the hepatic necrosis (p < 0.001). CONCLUSION: The results of this study demonstrated that pretreatment with IPC improved tissue ATP, EC, and hepatic necrosis at late stages of ischemia reperfusion injury of the liver. Increased nitric oxide, reduced MDA and arginase activity seemed to play a regulatory role in this delayed protective effect of IPC.     

Preconditioning the diabetic heart: the importance of Akt phosphorylation

Conflicting evidence exists whether diabetic myocardium can be protected by ischemic preconditioning (IPC). The phosphatidylinositol 3-kinase (PI3K)-Akt pathway is important in IPC. However, components of this cascade have been found to be defective in diabetes. We hypothesize that IPC in diabetic hearts depends on intact signaling through the PI3K-Akt pathway to reduce myocardial injury. Isolated perfused Wistar (normal) and Goto-Kakizaki (diabetic) rat hearts were subjected to 1) 35 min of regional ischemia and 120 min of reperfusion with infarct size determined; 2) preconditioning (IPC) using 5 min of global ischemia followed by 10 min of reperfusion performed one, two, or three times before prolonged ischemia; or 3) determination of Akt phosphorylation after stabilization or after one and three cycles of IPC. In Wistar rats, one, two, and three cycles of IPC reduced infarct size 44.7 +/- 3.8% (P < 0.05), 31.4 +/- 4.9% (P < 0.01), and 34.3 +/- 6.1% (P < 0.01), respectively, compared with controls (60.7 +/- 4.5%). However, in diabetic rats only three cycles of IPC significantly reduced infarction to 20.8 +/- 2.6% from 46.6 +/- 5.2% in controls (P < 0.01), commensurate with significant Akt phosphorylation after three cycles of IPC. To protect the diabetic myocardium, it appears necessary to increase the IPC stimulus to achieve the threshold for cardioprotection and a critical level of Akt phosphorylation to mediate myocardial protection.     

Protein kinase C and G(i/o) proteins are involved in adenosine- and ischemic preconditioning-mediated renal protection

Renal ischemic reperfusion (IR) injury is a significant clinical problem in anesthesia and surgery. Recently, it was demonstrated that both renal ischemic preconditioning (IPC) and systemic adenosine pretreatment protect against renal IR injury. In cardiac IPC, pertussis toxin-sensitive G-proteins (i.e., G(i/o)), protein kinase C (PKC), and ATP-sensitive potassium (K+(ATP)) channels are implicated in this protective signaling pathway. The aim of this study was to elucidate the signaling pathways that are responsible for renal protection mediated by both IPC and adenosine pretreatment. In addition, because A1 adenosine receptor antagonist failed to block renal IPC, whether activation of bradykinin, muscarinic, or opioid receptors can mimic renal IPC was tested because these receptors have been implicated in cardiac IPC. Rats were acutely pretreated with chelerythrine or glibenclamide, selective blockers of PKC and K+(ATP) channels, respectively, before IPC or adenosine pretreatment. Some rats were pretreated with pinacidil (K+(ATP)channel opener), bradykinin, methacholine, or morphine before renal ischemia. Twenty-four h later, plasma creatinine was measured. Separate groups of rats received pertussis toxin intraperitoneally 48 h before being subjected to the above protective protocols. IPC and adenosine pretreatment protected against renal IR injury. Pretreatment with pertussis toxin and chelerythrine abolished the protective effects of both renal IPC and adenosine. However, glibenclamide pretreatment had no effect on either renal IPC or adenosine-induced renal protection, indicating no apparent role for K+(ATP) channels. Moreover, pinacidil, bradykinin, methacholine, and morphine failed to protect renal function. Therefore, the conclusion is that cellular signal transduction pathways of renal IPC and adenosine pretreatment in vivo involve G(i/o) proteins and PKC but not K+(ATP) channels. Unlike cardiac IPC, bradykinin, muscarinic, and opioid receptors do not mediate renal IPC.     

Impact of ischemic preconditioning on dynamics of homing of endothelial progenitor cells after renal ischemia reperfusion injury

Objectives To investigate the impact of ischemic preconditioning (IPC) on dynamics of homing of endothelial progenitor cells (EPCs) after renal ischemia reperfusion injury (IR). Methods Sixty male Sprague-Dawley rats were randomly divided into three groups after right-side kidney nephrectomy: for sham-operated rats, lumbotomy without vascular clamping was performed; IR rats were clamped renal blood vessels for 40 minutes while IPC rats were pre-treated with 15 min ischemia and 10 min reperfusion. At 3, 12, 24 h, and 3 days after reperfusion, the pool of circulating, kidneys, lungs and spleens were harvested. The extent of renal injury was assessed by biochemical and histological examination. The dynamics of homing of EPCs was observed by flow cytometry. Results The rats in IPC group exhibited significant improvements in renal function and morphology. Compared with IR group and sham group, the number of EPCs in blood was increased in the IPC group at 12 h and 24 h after reperfusion (P＜0.05). The number of EPCs in kidney was increased at all times point in the IPC group and IR group as compared to the sham group (P＜0.05. In addition, EPCs number was increased in IPC group compared with the IR group at 12 h and 24 h [(11.36±0.66)% vs (6.37±0.69)%, (6.31±0.70)% vs (4.40±0.60)%, all P＜0.05]. Compared with IR group and sham group, the number of EPCs in the lung was increased in the IPC groups at 12 h after reperfusion [(2.95±0.66)% vs (1.78±0.59)%, (1.66±0.61)%, all P＜0.05]. The number of EPCs in spleen was increased in the IPC group at 72 h as compared with the IR group and sham group [(0.55±0.06)% vs (0.34±0.07)%, (0.31±0.06)%, all P＜0.05]. Conclusions Endogenous EPCs may home to injured kidney after IPC. EPCs can also gather in the lungs and spleen.     

异氟醚和卡托普利联合预处理对兔心肌缺血-再灌注细胞超微结构的影响

目的观察异氟醚、卡托普利联合预处理对兔心肌缺血-再灌注心肌细胞超微结构的作用。方法新西兰大白兔48只,随机均分为六组:假手术组(S组)、单纯缺血-再灌注组(IR组)、缺血预处理组(IPC组)、异氟醚组(I组)、卡托普利组(C组)和异氟醚、卡托普利联合预处理组(IC组)。采用结扎冠状动脉左前降支法制备兔心肌缺血-再灌注模型。观察各组心肌细胞超微结构变化。结果 IPC组心肌细胞损伤轻于IR组,IC组损伤最轻。结论异氟醚、卡托普利联合预处理对缺血-再灌注兔心肌细胞超微结构有更好的保护作用。     

Effect of ischemic preconditioning on hepatic microcirculation and function in a rat model of ischemia reperfusion injury

Ischemic preconditioning (IPC) may protect the liver from ischemia reperfusion injury by nitric oxide formation. This study has investigated the effect of ischemic preconditioning on hepatic microcirculation (HM), and the relationship between nitric oxide metabolism and HM in preconditioning. Rats were allocated to 5 groups: 1. sham laparotomy; 2. 45 minutes lobar ischemia followed by 2-hour reperfusion (IR); 3. IPC with 5 minutes ischemia and 10 minutes reperfusion before IR; 4. L-arginine before IR; and 5. L-NAME + IPC before IR. HM was monitored by laser Doppler flowmeter. Liver transaminases, adenosine triphosphate, nitrites + nitrates, and guanosine 3'5'-cyclic monophosphate (cGMP) were measured. Nitric oxide synthase (NOS) distribution was studied using nicotinamide adeninine dinucleotide phosphate (NADPH) diaphorase histochemistry. At the end of reperfusion phase, in the IR group, flow in the HM recovered partially to 25.8% of baseline (P < .05 versus sham), whereas IPC improved HM to 49.5% of baseline (P < .01 versus IR). With L-arginine treatment, HM was 31.6% of baseline (NS versus IR), showing no attenuation of liver injury. In the preconditioned group treated with L-NAME, HM declined to 10.2% of baseline, suggesting not only a blockade of the preconditioning effect, but also an exacerbated liver injury. Hepatocellular injury was reduced by IPC, and L-arginine and was increased by NO inhibition with L-NAME. IPC also increased nitrate + nitrate (NOx) and cGMP concentrations. NOS detected by NADPH diaphorase staining was associated with hepatocytes and vascular endothelium, and was induced by IPC. IPC induced NOS and attenuated HM impairment and hepatocellular injury. These data strongly suggest a role for nitric oxide in IPC. (Liver Transpl 2002;8:1182-1191.)     

缺血预处理对大鼠肺组织中缺血再灌注损伤相关基因表达的影响

目的 探讨缺血预处理(IPC)后大鼠肺组织中缺血再灌注损伤(IRI)相关基因的表达,为研究IPC减轻IRI的分子机制提供依据.方法 将雄性Wistar大鼠随机分为三组,缺血预处理组(IPC组,n:20)阻断左肺门5 min,开放10 min,如此重复3次,然后阻断左肺门,1 h后恢复血流灌注;缺血再灌注组(IR组,n=20)直接阻断左肺门,1 h后开放血流;假手术组(n=5)仅松解肺下部韧带,不做其它处理.IPC组和IR组分别于再灌注后1、3、6及24 h各取大鼠5只,切取左肺组织,采用含有22 226个大鼠基因点的Illumina RatRef-12全基因组表达谱微珠芯片检测肺组织中基因表达情况,比较IPC组与IR组各再灌注时间点基因表达的差异.结果 与IR组再灌注1 h相比,IPC组再灌注1 h时有1849个基因表达发生改变,其中上调的有918个,下调的有931个.与IR组再灌注3 h相比,IPC组再灌注3 h时有2568个基因表达发生改变,其中上调的有1377个,下调的有1191个.与IR组再灌注6 h相比,IPC组再灌注6 h时有1370个基因表达发生改变,其中上调的有563个,下调的有807个.与IR组再灌注24 h相比,IPC组再灌注24 h时仅有77个基因表达发生改变,全部为下调.结论 IPC对缺血再灌注损伤肺组织中基因表达的影响主要在再灌注后6 h内,以3 h最为明显;IPC可能通过影响凋亡相关基因、氧化应激相关基因、炎症反应及循环相关基因、能量代谢相关基因的表达来减轻IRI.     

Role of protein kinase C in intestinal ischemic preconditioning

INTRODUCTION: Tissue protection by ischemic preconditioning (IPC) has been previously characterized in organs such as the heart and involves at least in part PKC activation. It is not yet clear whether such preconditioning against ischemia/reperfusion (I/R) injury operates in the intestine, and, if so, whether IPC involves protein kinase C (PKC). MATERIALS AND METHODS: IPC of the small intestine in male Sprague Dawley rats was induced by 10-min superior mesenteric artery (SMA) clamp followed by 120-min reperfusion. Sham-operated control or IPC rats were then rechallenged with 20-min SMA clamp. Histological injury to jejunal mucosa was assessed by microscopic examination and Parks' injury score (Grade 0-4; 0 = no damage). PKC activity was determined by immunoprecipitation of specific isoforms followed by in vitro kinase assay using mucosal scrapings of the harvested jejunum. Data were expressed as mean +/- SEM and analyzed by one-way ANOVA with multiple comparison tests. RESULTS: Ten-minute SMA clamp led to epithelial damage that was fully reversed by 120-min reperfusion. Activity of several PKC isoforms (PKCalpha, -delta, -epsilon) increased after 10-min ischemia. Epithelial injury associated with 20-min SMA clamp was attenuated by prior IPC. The protective effect of IPC on intestinal mucosa was prevented when animals were pretreated with the conventional (c) and novel (n) PKC inhibitor Go6850, but not with Go6976 (selective cPKC inhibitor), rottlerin (selective PKCdelta inhibitor), or saline control. CONCLUSIONS: Brief mesenteric ischemia induces a reversible epithelial injury in rats associated with activation of several PKC isoforms. Injury induced by mesenteric ischemia is reduced by brief ischemic preconditioning, an effect that is abolished by nonselective PKC inhibition but not by a selective inhibitor of cPKC or PKCdelta. The results suggest that activation of nPKC isoform(s), especially PKCepsilon during and following ischemic insults (IPC), may play an important role in protection against I/R injury in the intestine.     

迷走神经电刺激后处理对大鼠心肌缺血/再灌注损伤的影响

目的 评价迷走神经电刺激后处理对大鼠心肌缺血/再灌注损伤的影响.方法 雄性SD大鼠40只,体重250 g～350 g,采用计算机产生的随机数平均分为4组(每组10只):假手术组(S组)、缺血/再灌注组(IR组)、缺血预处理组(IPC组)和迷走神经电刺激后处理组(POES组).除S组外,其余各组均结扎冠状动脉左前降支30...     

硫化氢预处理延迟相对大鼠心肌缺血-再灌注损伤的保护作用

目的探讨硫化氢预处理延迟相对大鼠心肌缺血-再灌注损伤的保护作用。方法将30只健康成年SD雄性大鼠随机分为三组:假手术组(S组)、缺血-再灌注组(IR组)和硫化氢组(H组)。S组仅开胸并分离冠状动脉左前降支,但不阻断血流150min;IR组行冠状动脉左前降支阻断30min,再灌注120min;H组予以静脉注射NaHS0.05mg/kg,给药后24h同IR组处理。再灌注结束后检测血清超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量和心肌梗死面积,电镜观察各组心肌细胞超微结构变化。结果与IR组比较,H组MDA含量降低,SOD活性增高(P<0.05),心肌梗死面积减少(P<0.05),电镜下H组心肌细胞损伤程度减轻。结论硫化氢预处理延迟相对大鼠缺血-再灌注心肌具有保护作用,与抗氧化反应有关。     

α7烟碱样乙酰胆碱受体激动剂后处理对大鼠在体心肌缺血/再灌注损伤的影响

目的 观察α7烟碱样乙酰胆碱受体(α7 nicotinic acetylcholine receptor,α7nAChR)激动剂后处理对大鼠在体心肌缺血/再灌注损伤(ischemia reperfusion injurv,IRI)的影响.方法 将40只SD大鼠采用计算机产生随机数法平均分为假手术组(S组)、缺血/再灌注组(IR组)、缺血预处理组(IPC组)和α7nAChR激动剂后处理组(PNU组),每组10只.实验中记录缺血期和再灌注初期心律失常,测定冉灌注30 min和180 min时的肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)、白介素-6(interleukin-6,IL-6)、高迁移率组蛋白1(high mobilitv group box 1 protein,HMGB1)和肌钙蛋白Ⅰ(troponin Ⅰ,TnI)血清浓度,实验结束取心脏,采用伊文思蓝和1%TTC双重染色法测量心肌梗死面积.结果 IR组,IPC组和PNU组的心肌梗死面积值分别为(78.4±16.1)%、(35.3±9.4)%和(60.4±7.0)%,且3组的TnI血清浓度分别为(1.02±0.12)μg/L,(0.25±0.03)μg/L和(0.17±0.04)μg/L与IR组相比,IPC组和PNU组心肌梗死面积(infarct size,IS%)显著减小、TnI血清浓度显著降低,IPC组灌注30min时TNF-α、IL-6血清浓度以及再灌注180 min时TNF-α和HMCB1血清浓度显著降低,PNU组再灌注30 min和180 min时TNF-α、IL-6和再灌注180 min时HMCB1血清浓度显著降低.与IPC组相比,PNU组IS%显著增大,但血清TnI浓度显著降低,冉灌注30 min时TNF-α血清浓度以及再灌注180 min时TNF-α、IL-6和HMCB1血清浓度显著降低,但再灌注30 min时IL-6血清浓度显著升高.结论 在大鼠在体心肌缺血/冉灌注损伤模型,α7nAChR激动剂后处理可通过抑制炎症反应获得心肌保护效应、但其心肌保护效应较缺血预处理弱.     

Microvascular protection induced by late preconditioning was abolished in STZ-induced acute diabetic rats

The authors attempted to determine whether ischemic preconditioning (IPC) can provide microvascular protection in skeletal muscle of diabetic rats against injury from a subsequent (24 hr later) prolonged period of ischemia and reperfusion. Male Sprague Dawley rats weighting 80 to 100 g were injected intraperitoneally with either streptozotocin (STZ, 65 mg/kg) or vehicle (sodium citrate, pH 4.5). Rats with a fasting blood glucose level over 300 mg/dl 1 week after injection of STZ were considered acute diabetic. The cremaster muscle of the rats underwent 45 min of IPC and 24 hr later, 4 hr of warm ischemia followed by reperfusion (I/R). Four groups were compared: IPC in normal rats (n=8); sham IPC in normal rats (n=8); IPC in diabetic rats (n=6); and sham IPC in diabetic rats (n=4). Microvascular responses in the cremaster muscle to IPC were determined by measuring the diameter of feeding, terminal arterioles and capillary perfusion using intravital microscopy, and by the evaluation of the endothelium-dependent nitric oxide system in the terminal arterioles. The average diameter of the feeding and terminal arterioles, as well as capillary perfusion, were significantly decreased in diabetic animals, compared to normal animals. There was a significant endothelial dysfunction detected in the terminal arterioles of diabetic rats. Ischemic preconditioning provided significant microvascular protection against prolonged ischemia/reperfusion in normal rats, but not in diabetic rats. IPC-induced microvascular protection in the normal skeletal muscle was abolished in STZ-induced acute diabetic rats.     

Role of PKC in the late phase of microvascular protection induced by preconditioning

INTRODUCTION: We hypothesized that the late phase of microvascular protection induced by ischemic preconditioning or by adenosine is protein kinase C (PKC) dependent. MATERIALS AND METHODS: The cremaster muscle of male Sprague-Dawley rats underwent 45 min of ischemic preconditioning and, 24 h later, 4 h of warm ischemia followed by 60 min of reperfusion. To mimic the effects of IPC, adenosine (ADO; an adenosine receptor agonist) or 4-phorbol 12-myristate 13-acetate (PMA; a PKC activator) was delivered to the vascular network of the cremaster 24 h before the prolonged ischemia via local intra-arterial infusion. To block the microvascular protection induced by ADO or IPC, chelerythrine (CHE; a PKC blocker) was given by local intra-arterial infusion prior to the administration of ADO or the initiation of IPC. Microvascular responses in the cremaster muscle to ischemic preconditioning or pharmacological preconditioning were determined by measuring terminal arteriole diameter and capillary perfusion using intravital microscopy and by the evaluation of the endothelium-dependent nitric oxide system in terminal arterioles. RESULTS: Blockade of PKC using CHE on day 1 eliminated both ADO- and IPC-induced microvascular protections seen on day 2. However, the microvascular protection induced by the administration of PMA (without IPC) that was given 24 h before the 4 h of warm ischemia/reperfusion was significantly better than the control group response (sham IPC), but was not as good as the protection induced by IPC or ADO alone. CONCLUSION: The overall results from these studies suggest that ischemic or ADO preconditioning induces late-phase microvascular protection in skeletal muscle by a PKC-dependent mechanism.